Discussion Of The Prior Art
Compositions for simultaneously achieving detergency and an appreciable level of softness in the machine laundering of fabrics, and thus suitable for use in the wash cycle, are well-known and widely available commercially. The fugitive interaction between anionic surfactant, perhaps the most commonly used of the available types of surfactants, and cationic softeners, particularly those of the di-lower-di-higher alkyl quaternary ammonium type, is likewise well recognized in the patent literature. Such interaction often results in the formation of unsightly precipitates which become entrapped within or otherwise deposit upon the fabric being washed. Discoloration or other aesthetically displeasing effects are for the most part inevitable. The net result is often a depletion in the effective amount of anionic available for useful purposes since the loss of anionic is the primary consequence.
Remedial techniques heretofore proposed to abate the aforedescribed cationic-anionic problem though divergent as to approach seem convergent as to result namely, less than satisfactory. Thus, although the most effective types of cationic quaternary ammonium softeners, as exemplified by the aforementioned di-higher alkyl type quats, such as distearyl dimethyl ammonium chloride, can function in the wash cycle in the presence of anionic, builder, etc., the quantity needed to achieve effective softening is usually coterminous with amounts promotive of undesired cationic-anionic interaction. As a general rule, at least about twice as much cationic is required for softening as for antistat.
In U.S. Pat. No. 3,325,414, dealing primarily with detergents of controlled foam or sudsing capability, the cationic-anionic problem and attendant detrimental effects are discussed in detail. The patent additionally points out that certain quaternary ammonium compounds, among the class of cationic agents, are generally unstable when heated and when in contact with alkaline builders, the instability being manufactured by the development of strong amine odors and undesirable color. The compositions of the patent are limited to the use of quaternary ammonium halides having but one higher alkyl group, the given structural formula for the cationic being correspondingly limited. Cationics of this type are markedly inferior to the di-higher alkyl types at least insofar as fabric softening activity is concerned.
Other prior art teachings at least tactically avoid the use of cationic softeners altogether proposing the use of, for example, anionic materials as softening agents. U.S. Pat. No. 3,676,338 is representative, this patent teaching the use of anionic softener referred to as "branched-chain carboxylic acids," as fabric softener. Presumably, anionic detergent would be stable in the presence of the anionic softener.
As the foregoing demonstrates, the remedies proposed necessitate the discarding of softeners and principally those of the di-higher-di-lower alkyl quaternary ammonium salt and cyclic imide types, these having been determined by experience to be among the most effective softeners thus far developed in the art.
In the above mentioned U.S. Pat. No. 4,230,590, heavy duty detergents comprising conventional builder, principally anionic surfactant components, cationic softener and a mixture of fatty acid soap and cellulose ether are disclosed. The soap-cellulose ether mixture is in the form of a spaghetti, flake or other shape and is present in the composition as substantially homogeneously dispersed, discrete particles.
In U.S. Application Ser. No. 96,370, filed Nov. 21, 1979, heavy duty detergents having compositions similar to that described in the preceeding paragraph with the exception that cellulose ether is excluded therefrom are disclosed.
Although the above mentioned soap and cationic softener containing detergent compositions possess desirable softening and detersive properties, it has been found that the solubility of such compositions is low, particularly in cold laundering temperatures. As a result, the compositions cannot be effectively used in cold water.